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When accessing a remote branch (specified as an URL), it may occur that the
server requests an authentication.

This authentication can be provided in different ways:

1. Embedding the user and password
in the URL:

bzr branch <scheme>://<user>:<password>@host:port/path

scheme: Any transport protocol requiring authentication.

user: The login used to authenticate.

password: The associated password.

host: The address of the server.

port: The port the server is listening to.

path: The path on the server.

2. Embedding the user in the URL and let bzr find the right password or prompt
for one:

bzr branch <scheme>://<user>@host/path

3. Embedding nothing in the URL and let bzr find user and password or prompt
for user and/or password:

bzr branch <scheme>://host/path

This specification proposes a mechanism that will allow users to
just use bzrbranch<scheme>://host/path or bzrbranch<scheme>://<user>@host/path and leaves bzr find the user
and password in its configuration files.

When no user is specified for FTP, SFTP or SSH, the actual behavior
of bzr is to default to getpass.get_user().

Any implementation of this specification should respect that behaviour.

This specification also proposes a way to describe credentials so that several
remote branches can use the same definition. This is particularily important
for users handling a lot of passwords and who need to update them on a regular
basis.

Embedding user and passwords in the command line is a security
hazard (see bug #34685).

Storing passwords in ~/.bazaar/bazaar.conf or ~/.bazaar/locations.conf
is also a security risk.

Typing user and passwords is error-prone and boring.

Yet, a safe way to store passwords, while allowing bzr to retrieve them, when
needed, could improve the bzr user experience.

This specification describes a way to provide user and passwords to bzr while
storing them in a relatively safe way.

Note that SSH servers can be configured to use keys instead of (user,
password) and, when used with appropriate agents, provide the same kind of
comfort this specification aims to provide for all other schemes. Since SSH
agents provide a safer way to secure the passwords, this specification is
restricted to providing user but does not provide password when used
for SSH.

There are two kinds of authentication used by the various schemes supported by
bzr:

user and password

FTP and SFTP needs a (user, password) to authenticate against a
host (SFTP can use SSH keys too, but we don’t talk about that in this
specification as SSH agents provide a better solution).

user, realm and password

HTTP and HTTPS needs a (user,realm,password) to authenticate
against a host. But, by using .htaccess files, for example, it is possible
to define several (user,realm,password) for a given host. So what is
really needed is (user, password, host, path). The realm
can be ignored [1] as long as it is still presented to the user
when prompting for the password (unless someone found a way to declare two
different realms for the same path).

HTTPproxy can be handled as HTTP (or HTTPS) by explicitly
specifying the appropriate port.

The true purpose of realms is to allow the same credentials
to be reused for disjoint hierarchies. Ignoring them in this specification
aims to simplify the user experience while still allowing to share the same
credentials for a whole hierarchy.

To take all schemes into account, the password will be deduced from a set of
authentication definitions (scheme, host, port, path, user,
password).

scheme: can be empty (meaning the rest of the definition can be used
for any scheme), SFTP and bzr+ssh should not be used here, ssh
should be used instead since this is the real scheme regarding
authentication,

host: can be empty (to act as a default for any host),

port can be empty (useful when an host provides several servers for the
same scheme), only numerical values are allowed, this should be used only
when the server uses a port different than the scheme standard port,

path: can be empty (FTP or SFTP will never use it),

user: can be empty (bzr will defaults to Python’s
getpass.get_user() for FTP, SFTP and SSH),

password: can be empty (for security reasons, a user may use the
definitions without storing the passwords but want to be prompted ; or the
password will be provided by an external plugin via the
password_encoding mechanism decribed below). Must be left empty for
ssh.

password_encoding: can be empty (default is plaintext).

Also note that an optional verify_certificates=no field will allow the
connection to HTTPS hosts that provides a self certified certificate (the
default should be to refuse the connection and inform the user). (Not
implemented yet)

Multiple definitions can be provided and, for a given URL, bzr will select a
(user [, password]) based on the following rules :

the first match wins,

empty fields match everything,

scheme matches even if decorators are used in the requested URL,

host matches exactly or act as a domain if it starts with ‘.’
(project.bzr.sf.net will match .bzr.sf.net but projectbzr.sf.net
will not match bzr.sf.net).

port matches if included in the requested URL (exact matches only)

path matches if included in the requested URL (and by rule #2 above,
empty paths will match any provided path).

An optional password_encoding field may specify how the password is encoded
but has no impact on the definition selection.

Possible values are plaintext (no encoding at all) and base64. When the
field is absent, plaintext is assumed. Additional encodings may be added in
future versions.

Encoding passwords in base64, while weak, provides protection against
accidental reading (if an administrator have to look into the file, he will not
see the passwords in clear).(Not implemented yet).

This specification intends to ease the authentication providing, not to secure
it in the best possible way.

Plugins can provide additional password encodings. The provided
netrc_credential_store plugin can be used as an example implementation.

Future versions of this specification may provide additional
encodings [2].

Additional password encoding methods may be defined
that will rely on external means to store the password which, in these
cases, will not appear anymore in the definition. It is assumed that
additional password encodings will provide a storage outside of the file
described here. The netrc encoding, for example, provides passwords by
retrieving them from the .netrc file.

Even if ~/.bazaar/bazaar.conf and ~/.bazaar/locations.conf seems to
provide most of the needed infrastructure, we choose to use a dedicated file
for the authentication info ~/.bazaar/authentication.conf for the following
reasons:

allow the user to protect the content of one file only, relaxing security
constraints on the others,

while locations.conf is organized around local branches,
authentication.conf is organized around remote branches or more
generally servers. The same authentification definition can even be used
for several schemes for servers providing those schemes.

~/.bazaar/authentication.conf will use the same file format as
~/.bazaar/bazaar.conf.

Each section describes an authentication definition.

The section name is an arbitrary string, only the DEFAULT value is reserved
and should appear as the last section.

Each section should define:

user: the login to be used,

Each section could define:

host: the remote server,

port: the port the server is listening,

verify_certificates: to control certificate verification (useful
for self certified hosts). This applies to HTTPS only. Accepted values
are yes and no, default to yes.

path: the branch location,

password: the password,

password_encoding: the method used to encode the password if any,

The default content of the file will be:

[DEFAULT]

This section could define:

user: default user to be used (if not defined the usual
bzr way applies, see below).

all connections are done with the same user (the remote one for which
the default bzr one is not appropriate) and the password is always prompted
with some exceptions:

# Pet projects on hobby.net[hobby]host=r.hobby.netuser=jimpassword=obvious1234# Home server[home]scheme=httpshost=home.netuser=joepassword='c2VjcmV0LXBhc3M='password_encoding=base64verify_certificates=no# Still searching a free certificate provider[DEFAULT]# Our local user is barbaz, on all remote sites we're known as foobaruser=foobar

bzr should be able to prompt for a user for a given (scheme, host
[, realm]). Note that realm is available only after a first
connection attempt to the server.

No assumptions should be made about the clients of this service
(i.e. Transport is the primary target but plugins must be able to use it as
well, the definitions used: (scheme,host,[port,]path) are general
enough to described credentials for svn servers or LaunchPad XML-RPC
calls).

Policies regarding default users may be taken into account by the
implementations, there is no good way to represent that in this specification
and stays flexible enough to accommodate various needs (default user policies
may differ for different schemes and that may be easier to handle in the code
than in the authentication file itself).

If no user can be found by the mechanism described above, bzr should still
default to getpass.get_user() and may attempt a second matching to obtain
a password.

As this specification proposes a matching between some credentials
definitions and real URLs, the implementation provides an optional UI
feedback about which credential definition is used. Using -Dauth will
output some traces in the .bzr.log file metionning the sections
used. This allows the user to validate his definitions.

Automatic (one-time) conversions may be proposed if sufficient demand
exists,

What if a .netrc file exists ?

It is honored if the definition specifies
password_encoding=netrc.

What mode should the authentication file use ?

600 read/write for owner only by default, if another mode (more
permissive) is used, a warning will be issued to inform the users of the
potential risks.(Not implemented yet)

What about using seahorse on Ubuntu or KeyChainAccess on Mac OS X ?

plugins can be written and registered to handle the associated
password_encoding.

Could it be possible to encode the whole authentication file with an SSH key
?

yes and if the user configure a ssh-agent it will not be queried for
pass-phrase every time we want to query the file for a password. But
that seems a bit extreme for a first version.(Not implemented yet and
may be never)

Why can’t bzr update the authentication file when it queried the user for a
password ?

a future version may address that but:

1. The user may want to decide which passwords are stored in the file and
which aren’t.

2. The user should decide if the passwords are encoded (and how) or not
(but we may default to base64).

3. The right definition may be hard to get right, but reducing it to
(scheme,host,[port,]user,password) may be a good start. I.e. no
path so that all paths on the host will match. The user will have to
modify it for more complex configurations anyway.